Fertilizer Recommendation Tables - 2007 Revision

Nitrogen Soil Test For Corn

In 1991, the Ontario Soil Management Research and Services Committee approved the use of a spring nitrate nitrogen test for corn in Ontario. In 1998, the recommendations were changed to reflect the nitrate-nitrogen in the 0-30 cm depth (top one foot), and to include samples collected at pre-sidedress timing (early June) as well as pre-plant.

The test will reflect the nitrogen contribution from legumes plowed down in the fall or fall-applied manure. It may not adequately measure the nitrogen from crop residues or manures plowed down in the spring close to the time of sampling.

The recommended rates shown here are based on a nitrogen/corn price ratio of 5 (i.e. the price per kg of actual N applied is 5 times the price of a kg of grain corn). For a price ratio of seven, the nitrogen recommendations should be decreased by approximately 20 kg N/ha. For a price ratio of three, the nitrogen recommendations should be increased by approximately 30 kg N/ha.

Spring nitrate nitrogen refers to samples taken within five days of planting (either before or after)

Presidedress nitrate nitrogen refers to samples taken when the corn is six to twelve inches tall (usually within the first two weeks of June).

Conversion Factors

To convert from kg/ha of nitrate-N to ppm for a 30 cm sample, divide kg/ha by 4.

For example, if the nitrate nitrogen content of a sample taken from the top 30 cm of soil is 32 kg/ha, the nitrate nitrogen concentration is 32 kg/ha ÷ 4 = 8 ppm